Field of the Invention
This invention relates to switches and has particular reference to pilferage detecting switches intended for burglar alarms or the like.
In pilferage type burglar alarms, small and unobtrusive switches are placed under certain selected objects and are connected in circuit with an alarm system so that when an object is removed the alarm will be set off. Heretofore, such switches were constructed as normally open switches in order to make them as thin as possible and, as such, generally comprised two separate leaf spring contacts which, when an object was placed thereon, closed a circuit and when the object was removed, opened the circuit.
Although such switches work satisfactory, they require a normally completed alarm circuit, i.e., a circuit which, when in a quiescent state, requires constant electric current to be passed therethrough and which, when the circuit is broken, sets off an alarm.
As is well known, it is normally desirable to employ self-contained burglar alarm circuits, using batteries as the power source, so that cutting of the power lines will not deactivate the alarm circuit. Therefore, in using switches of the above normally open type, a constant current drain is applied to the batteries, requiring repeated replacement or recharging thereof.